﻿/*
	Copyright (C) 2019 Zongming Liu <1849059316@qq.com>

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.
	
	You should have received a copy of the GNU General Public License along
	with this program; if not, write to the Free Software Foundation, Inc.,
	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#ifndef Singleton_h__
#define Singleton_h__

#include "NonCopyable.h"
#include <cassert>

namespace SkyEngine2d
{
	
	/*!
	 \brief 单例对象的基类
	 \tparam T 单例类的类型
	 \tparam is_auto_create 是否在获取单例对象时自动创建对象
	 \example Exp_singleton.cpp
	*/
	template <typename T,bool is_auto_create = true>
	class Singleton
		:public NonCopyable
	{
	public:
		virtual ~Singleton()
		{
		}

		//! 获取单例对象的实例
		/*!
		\return T*  
		*/
		static T* getInstance()
		{
			static T t;
			return &t;
		}
	protected:
		Singleton()
		{
		}
	};


	template<typename T>
	class Singleton<T,false>
		:public NonCopyable
	{
		static T* s_instance;
	public:
		Singleton()
		{
			assert(!s_instance&&"已经构造该对象");
			s_instance = (T*)(this);
		}

		virtual ~Singleton()
		{
			assert(s_instance&&"对象没有创建");
			s_instance = nullptr;
		}
		//! 获取单例对象的实例
		/*!
		\return T*
		*/
		static T* getInstance()
		{
			return s_instance;
		}
	};

	template<typename T>
	__declspec(selectany) T* SkyEngine2d::Singleton<T, false>::s_instance = nullptr;
}

#define SINGLETON_CLASS(T) friend class Singleton<T>;

#endif // Singleton_h__
